xxxin SEED-DISPERSAL AND GEOLOGICAL TIME 507 



Much might be said of these matters, but it would be out of 

 place here ; and I will content myself with stating the view above 

 indicated that the suspension of the agencies of seed-dispersal over 

 the Pacific is probably connected with a general principle affecting 

 the whole plant-world. The tendency in the course of ages has 

 been towards the differentiation of climate, bird, and plant, the 

 range of the bird being largely controlled by the climate, and 

 the range of the plant being mainly dependent on the range of the 

 bird. 



It is evident that in some cases the plants themselves may 

 make the endemism of a flora more pronounced by creating their 

 own difficulties and by standing in the way of their own dispersal 

 to outside regions. It has been shown that some of the endemic 

 Hawaiian genera (see Note 68) have deteriorated in their capacity 

 for dispersal by birds ; and similar remarks are made with reference 

 to the genera Sicyos (page 365) and Eugenia (page 350). Genera 

 with stone fruits like Elaeocarpus possess in the different species 

 stones of various sizes, some of them suitable in point of size for 

 conveyance in a bird's body over an ocean, others so large that 

 one could only predicate for them a limited capacity for distribu- 

 tion by birds over a few hundred miles of sea. One, for instance, 

 could safely assume that species of Elaeocarpus, with stones an inch 

 and over in size, that occur in Fiji and Hawaii, are not suited for 

 distribution over an ocean now ; whilst other species found in New 

 Zealand and Rarotonga have stones less than half this size, which 

 are quite fitted for distribution by birds over broad tracts of ocean 

 (page 337). 



This brings us to discuss the relative difficulties presented from 

 the dispersal-standpoint by the forest floras of Hawaii, Fiji, and 

 New Zealand. It is with the forest floras that nearly all the 

 difficulties of distribution lie ; and I hope I shall not be considered 

 presumptuous, or at all events too heterodox, in expressing the 

 opinion that judging from the details given in Kirk's Forest Flora 

 of New Zealand those islands present no greater difficulties for the 

 student of plant-distribution, if we exclude the Coniferae, than 

 either Fiji or Hawaii. Indeed, even with the Conifers included, 

 New Zealand presents fewer problems than Fiji, and Hawaii has 

 its own special difficulties connected with the inland species of the 

 Leguminosae. There is, on the other hand, no special New Zealand 

 difficulty. It possesses the Conifers in common with Fiji ; and it 

 shares with Fiji and Hawaii genera like Elaeocarpus and Sider- 

 oxylon, that take a foremost place amongst the trees of the Pacific 



